The objectives of this project are to study, in the awake, freely behaving rat, the interaction of opiates on neuronal unit activity, how these responses are modified (conditioned) during the course of addiction, and the relationship between this phenomena and that of more subjective euphoria-rewarding aspects of the opiates. The first phase of the project is to determine if opiates will be self-administered directly into the brain. Preliminary evidence indicates that rats will self-administer morphine (as low as 0.1 micrograms/10 nl injection) into lateral ventricle, lateral hypothalamus and fourth ventricle. Negative results have been found from a number of additional brain sites. Acute, single unit studies (a prelude to the chronic recording-conditioning series), has shown opiate specific responses in lateral ventral medial hypothalamus, and dorsal medial thalamus. Significance of these findings relates to opiates' role in normal brain reward behavior and to maintenance of drug addiction.